Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, India.
Langmuir. 2011 Jul 19;27(14):8687-93. doi: 10.1021/la201471f. Epub 2011 Jun 23.
While forming layer-by-layer (LbL) electrostatic assembly of a magnetic organic molecule, namely, nickel phthalocyanine (NiPc), we apply a magnetic field. The field orients the magnetic moment of the molecules on a monolayer along the direction of magnetic field. Such an orientation of the molecules is then electrostatically immobilized with a monolayer of a polycation. By repeating the dipping cycle, we form LbL films with planar NiPc molecules facing a particular direction. With NiPc's moment perpendicular to the molecular plane, two types of LbL films were formed: (a) NiPc's molecular plane parallel to the substrate (moment is perpendicular) and (b) molecules perpendicular to the substrate and facing one particular direction, the direction of magnetic field. Such films, with the molecules lying either (a) parallel or (b) perpendicular to the substrate, provide unique systems to study anisotropy of optical, dielectric, and electrical characteristics in these planar organic molecules. The latter film responds to the polarization of incident beam in electronic absorption spectroscopy. Here we show methods to obtain an orientation of molecules in LbL films and study anisotropy of dielectric constant and conductivity of the molecules in ultrathin films.
在形成磁性有机分子（即镍酞菁（NiPc））的层层静电组装过程中，我们施加磁场。该磁场使单层分子的磁矩沿磁场方向排列。然后，通过单层聚阳离子静电固定这种分子的取向。通过重复浸渍循环，我们用面向特定方向的平面 NiPc 分子形成了 LbL 薄膜。由于 NiPc 的磁矩垂直于分子平面，因此形成了两种 LbL 薄膜：（a）NiPc 的分子平面平行于基底（磁矩垂直）和（b）分子垂直于基底并面向磁场的特定方向。这些具有分子平行（a）或垂直（b）于基底的薄膜提供了研究这些平面有机分子的光学、介电和电特性各向异性的独特系统。后者薄膜对电子吸收光谱中入射光束的偏振做出响应。在这里，我们展示了在 LbL 薄膜中获得分子取向的方法，并研究了超薄膜中分子的介电常数和电导率的各向异性。
